Immobilized microorganisms have been noticed in recent years because they may be used to realize efficient continuous fermentation in a bioreactor.
Many methods, including the entrapment method and physical adsorption method, have been known to date as microorganism immobilizing methods. Immobilization of a microorganism by the entrapment method, however, has a problem in that the cost greatly increases because it requires a complicated operation of wrapping a previously-cultured microorganism suspension in a macromolecular gel.
The physical adsorption method makes it possible to immobilize a microorganism merely by introducing a carrier into a microorganism suspension. Therefore, the method has an advantage in that the operation of entrapping a microorganism performed in the entrapment method is not necessary. Carriers such as activated carbon, porous glass, sellite, chitin, and cellulose are known as carriers used for the physical adsorption method.
However, because surface structures of these carriers are not suitable for attachment of microorganisms, there is a problem in that only a small number of microorganisms are attached, and there is a disadvantage in that it is difficult to cause a flow in a fermenter or bioreactor, depending on the type of carrier, because of its high specific gravity.
It is the first object of the present invention to provide a granular carrier for immobilizing microorganism cells, whose surface structure is suitable for attachment of a microorganism and whose specific gravity ranges between 1.00 and 1.20, and which does not lower the flowability in a fermenter or bioreactor.
Moreover, a device for manufacturing the above granular carrier is disclosed in, for example, the official gazette of Japanese Patent Laid-Open No. Hei 1-118529. According to the system disclosed in this official gazette, dripped granular gels are put in a Petri dish so that grains are lined up, and they are irradiated with ultraviolet radiation by a high-pressure mercury lamp while being vibrated.
Though this system realizes irradiation at a certain light intensity, it has a problem in that the production efficiency is very low because continuous production is impossible.
Moreover, the present inventor previously proposed a device for manufacturing grains by moving dripped granular gels by a transparent spiral tube and simultaneously irradiating the gels with active rays (official gazette of Japanese Patent Laid-Open No. Sho 60-106836).
The previously proposed system is described below by referring to FIG. 1. This system comprises a tank 18 for storing a liquid composition containing a photo-curable resin, polymerization initiator, and water-soluble polysaccharide capable of gelatinizing, a dripping unit 20 for dripping the liquid composition through a nozzle, and a gelatinizing vessel 22 for storing an aqueous medium containing polyvalent metal ions.
The liquid composition is supplied to the dripping unit 20 from the tank 18 through a transport tube 24. The dripping unit 20 stores a predetermined amount of liquid composition and has a nozzle 30 at the lower position so as to drip the liquid composition from the front end of the nozzle. A droplet of the liquid composition drops into the aqueous medium containing the polyvalent metal ion stored in the gelatinizing vessel 22 and is gelatinized, and, thereafter, is supplied to a light irradiation section 12 through a tube 31 connected to the bottom of the gelatinizing vessel 22.
When a liquid gel descends through a spiral transparent tube 34 together with the aqueous medium, it is irradiated with active rays emitted from an adjacently-arranged light source 32, and a photo-curable resin in particulate matter causes an optical reaction. The particulate matter, which has increased in strength due to the optical reaction, moves to a grain recovery section 14 and is stored in a recovery vessel. The aqueous medium is returned to the gelatinizing vessel 22 by a pump 48 and is repeatedly used.
This particulate matter-manufacturing system has superior advantages in that it realizes continuous production and light irradiation for a relatively long time.
However, it is clear that the system has the following problems to be solved:
(a) One light source (or more) is (or are) necessary for one tube, and the production efficiency is low. PA1 (b) Because a granular gel flows in a tube in almost a horizontal direction, the irradiation efficiency is lowered due to the screening effect because of crowded grains when there is a density difference between the a granular gel and a medium. Moreover, when the flow rate is increased to eliminate the crowdedness of grains, the tube length is increased and the system space increases. PA1 (c) When the transparent spiral tube is made of plastic, it is inferior in durability because deterioration due to ultraviolet radiation is accelerated. When the tube is made of glass, it is not easy to handle the tube when it is increased in size and the cost increases. PA1 (d) Because the batch system (taking out particulate matter when it is collected in the recovery vessel 40) is used, the particulate matter-ejecting operation is complex. PA1 (e) When taking particulate matter out of the recovery vessel 40, aqueous medium is also taken out. Therefore, it is necessary to separate the particulate matter from aqueous media and to replenish the recovery vessel with aqueous medium. PA1 a granular carrier for immobilizing microorganism cells having a surface suitable for attachment of a microorganism, characterized in that the carrier is obtained by dripping a liquid composition containing (a) a hydrophilic photo-curable resin having at least two ethylenically unsaturated bonds in one molecule, (b) photopolymerization initiator, and (c) water-soluble macromolecular polysaccharide capable of gelatinizing through contact with an alkaline metal ion or polyvalent metal ion, into an aqueous medium containing alkaline metal ions or polyvalent metal ions to gelatinize the composition, and irradiating the composition with active rays to cure it, said carrier having a specific gravity of 1.00 to 1.20, and a contact angle of 2.degree. to 30.degree. formed between the carrier surface and n-paraffin; and PA1 a particulate matter-manufacturing device comprising a gelatinizer for forming a granular gel by dripping a liquid composition containing (a) a hydrophilic photo-curable resin having at least two ethylenically unsaturated bonds in one molecule, (b) photopolymerization initiator, and (c) water-soluble macromolecular polysaccharide capable of gelatinizing through contact with an alkaline metal ion or polyvalent metal ion, into an aqueous medium containing alkaline metal ions or polyvalent metal ions to gelatinize the composition, and a light irradiator for forming particulate matter by irradiating a granular gel formed by the gelatinizer with ultraviolet radiation and curing the photo-curable resin in the granular gel, in which the light irradiator is provided with a light source and a plurality of transparent tubes which are almost vertically arranged closely to the light source, and in which the granular gel is moved. PA1 (i) Compounds having a photopolymerizable ethylenically-unsaturated group at the both ends of polyalkylene glycol such as:
In view of these problems, it is the second object of the present invention to provide a device for producing particulate matter containing a photo-curable resin as a granular carrier for immobilization, in large quantities and efficiently.